Living in one locale for more than 70 years has its advantages. Certainly, one of the pluses of staying put is seeing a once usual bird of your youth that became uncommon during your middle age become more common once again. Such is the case with the Cooper’s hawk (Accipiter cooperii).
During the 1940s, 50s and 60s in my slice of Ford County, Cooper’s hawks were far fewer than other raptors such as red-tailed hawks and American kestrels. But, if you knew their haunts, a Cooper’s could be spotted with a reasonable search. As the small woodlots and other woody habitats such as Osage orange hedgerows were bulldozed out and use of pesticides increased, numbers dwindled. Seeing one became a rarity. Cooper’s hawks were declared a state-endangered species in 1977. Thankfully, since then Cooper’s hawk numbers have increased; and in 1997, their state-listed status was removed.
Now, Cooper’s hawks are increasingly encountered, particularly in urban settings that have significant woody habitats. This change in venue may seem strange for this Accipiter. After all, their genus is classed as a forest raptor. Its move to town has some urbanites wondering what this hawklike bird with its distinctly barred flight feathers and long tail is—a hawk no doubt, but which one?
The Cooper’s is often confused with another Accipiter, the sharp-shinned hawk (Accipiter striatus). Although both have about the same in-flight silhouette, rounded short wings and a long slender tail, the Cooper’s, being a bit larger than a crow, is the larger of the two hawks. However, comparing sizes can be misleading. Why? Because within each species of Accipiter, the female is much larger than the male. Thus, the larger female sharp-shinned is often comparable in size to that of the smaller male Cooper’s. A somewhat reliable indicator is in-flight tail shape. The tail end of a Cooper’s is rounded, whereas that of a sharp-shinned is squared off. The head of the Cooper’s is larger in relation to its body than that of the sharp-shinned hawk.
The Cooper’s hawk historically nested in woody habitats in rural Illinois, but today is increasingly raising its clutches in town. Favorite urban settings for nesting include small groupings of mature white pines. Bird watchers who feed songbirds are encouraging Cooper’s to take up town living. Nothing draws this hawk like numerous congregations of singing birds. In areas of the state where intensive row-crop agriculture reigns and woody habitats have been mostly destroyed, urban Cooper’s hawks may outnumber their rural cousins.
Nests are not elaborate, but functional. Males do most of the nest building. Along with white pines, other favorite nesting trees include firs, spruces and oaks. Usually nests are built in the upper half of the tree, some 25 to 50 feet off the ground. Sometimes a Cooper’s pair uses an old squirrel or crow nest. From two to six white eggs are laid from mid-April through June. Eggs may exhibit a pale, bluish blush. The male hunts and provides most of the food for the female and hatchlings while they are on the nest. Smaller and medium-size birds such as cardinals, sparrows, woodpeckers, mourning doves, robins, and starlings, usually make up most of the diet. However, food fare includes just about any mammal, bird, reptile or amphibian a Cooper’s can tackle, such as gray squirrels, garter snakes, and even American toads. The hatchlings grow rapidly. Once fledged they stay for a short time in the family group and hone hunting skills under the watch of their parents.
A pair of Cooper’s hawks tends to be somewhat secretive when selecting nesting sites, but not always. Several years ago, a pair successfully nested about 30 feet up in a honey locust on the University of Illinois Quad just a few yards away from a main sidewalk. Thousands of students passed underneath daily. Rarely was the nest, its occupants, or all the activity of raising the clutch noticed. Apparently, the abundance of campus gray squirrels and mourning doves was just too beneficial for the pair of Cooper’s to pass up for breeding.
Cooper’s hawks can be extremely aggressive when pursuing prey. Once a Cooper’s locks in on prey, they seemingly discount all else and proceed with reckless abandon. A personal incident of mine stands out: As I was climbing over a woven-wire fence that was overgrown from both sides with young hackberry, black cherry and assorted brush, a robin came crashing through with a Cooper’s in hot pursuit. Neither had a clear flight path, or noticed me as they passed just an arm’s reach away. The Cooper’s was colliding with twigs and small branches. Such chases come at a cost. Wings and breasts take a beating. One study of Cooper’s hawk skeletons revealed that nearly one-fourth of breast bones had been broken and healed over. It could also be considered that some likely did not survive their prey-pursuit injuries and remained unaccounted for in this study making the injury incidence likely even higher. The Cooper’s is one tough bird!
Robert J. Reber is an emeritus faculty member in the Department of Food Science and Human Nutrition of the University of Illinois at Urbana–Champaign. He has been a lifelong student of many aspects of the Natural World, including archaeology. Bob has served as a managing editor and author for publications such as “The Illinois Steward” magazine and the “Illinois Master Naturalist Curriculum Guide.”